What Is an EIN Number and Do You Need One?

To get an EIN, apply directly with the IRS — it’s free, and the online application issues your nine-digit Employer Identification Number immediately once you finish the session. Skip any third-party site that charges a fee for what the IRS provides at no cost.¹ An EIN works like a Social Security number for a business: banks, the IRS, and state agencies use it to identify your entity.

Do You Actually Need One

Not every business owner needs an EIN, but several situations require one:²

You hire employees. Even one triggers the requirement, because employment taxes must be withheld and reported under a separate business tax account.
You operate a corporation or partnership. These entities need an EIN whether or not they have employees.
You run a multi-member LLC. The IRS treats it as a partnership by default, so it needs its own EIN.
You manage a trust (other than certain revocable trusts), estate, tax-exempt organization, or retirement plan.
You owe excise taxes on products like alcohol, tobacco, or firearms.

Sole proprietors with no employees, no excise tax obligations, and no retirement plan can generally use their personal Social Security number instead.³ Many still choose to get an EIN to keep their SSN off invoices and business paperwork.

Single-Member LLCs

A single-member LLC is a special case. The IRS treats it as a “disregarded entity” for income tax, meaning income and expenses flow to your personal return. If you have no employees and no excise tax obligations, you technically don’t need an EIN and can use your SSN for federal reporting. Once you hire employees, you must get an EIN and use it for employment tax reporting. You may also need one if your bank requires it to open a business account, or if your state requires a federal EIN for state tax registration.⁴

What to Have Ready Before You Apply

The application maps to the fields on Form SS-4. Have the following in front of you so you can finish in one sitting:⁵

The legal name of the entity, exactly as it appears on your articles of incorporation, partnership agreement, or other formation documents.
The responsible party’s name. This is the individual who owns or controls the entity and directly or indirectly manages its funds. The responsible party must be a natural person, not another business, unless the applicant is a government agency.⁶
The responsible party’s SSN or ITIN. Every EIN is linked to a personal taxpayer identification number.
Your business mailing address and, if different, the physical location.
The date the business started or was acquired. Trusts enter the date the trust was funded; estates enter the decedent’s date of death.
Your reason for applying, such as starting a new business, hiring employees, opening a bank account, or changing your business structure.

You can download a blank Form SS-4 from IRS.gov to review the fields ahead of time, even if you plan to apply online.⁵

Applying Online

The IRS online EIN assistant is the fastest route and it’s free. Answer the questions, and if you qualify, your EIN appears on screen at the end of the session. You can view, print, and save the confirmation right away.³

The tool is available during these hours, Eastern Time:

Monday through Friday, 6:00 a.m. to 1:00 a.m. the following day
Saturday, 6:00 a.m. to 9:00 p.m.
Sunday, 6:00 p.m. to 12:00 a.m.

Two limits to know. You have to complete the application in a single session; it expires after 15 minutes of inactivity, which forces you to restart. And the IRS limits each responsible party to one EIN application per day.³

The online tool is only open to applicants whose principal business, office, or legal residence is in the United States or a U.S. territory. Everyone else applies by phone, fax, or mail.⁷

Applying by Fax or Mail

If online isn’t an option, complete Form SS-4 and fax it to the IRS. Include a return fax number, and the IRS generally faxes your EIN back within four business days.⁷

Mail is the slowest. Expect roughly four to five weeks to receive your EIN by return mail, so plan accordingly if you have a deadline.⁷

Applying From Outside the U.S.

International applicants can apply by phone at 267-941-1099 (not toll-free), Monday through Friday, 6:00 a.m. to 11:00 p.m. Eastern Time. Have a completed Form SS-4 in hand before calling; an IRS representative will walk through the form with you and assign the number during the call. If the responsible party doesn’t have and isn’t eligible for an SSN or ITIN, write “foreign” or “N/A” on line 7b. The IRS may ask you to mail or fax a signed copy of the form within 24 hours after issuing the number.⁷

After the EIN Is Issued

The IRS sends a confirmation called the CP 575 notice, your official record of the assigned number. Online applicants print it at the end of the session; fax and mail applicants receive it by their chosen method. Keep it somewhere safe. You’ll need it for a business bank account, licensing, and tax filings.³

If a tax return comes due before your EIN arrives, write “Applied For” and the date you applied in the EIN space on the return. If a tax deposit is due, send the payment to the IRS service center for your state, made payable to “Internal Revenue Service,” with your name, address, type of tax, period covered, and the date you applied.⁸

Later Changes and Lost Numbers

Changing your business name or address doesn’t require a new EIN, but changing your legal structure or ownership generally does. Common triggers include a sole proprietor incorporating or forming a partnership, a corporation receiving a new charter or merging into a new corporation, a partnership incorporating or ending and restarting, and an LLC terminating to form a new corporation or partnership. A single-member LLC also needs a new EIN once it must start filing employment or excise taxes.⁹

For a change to your mailing address, physical location, or responsible party, file Form 8822-B instead. A responsible-party change must be reported within 60 days, and processing generally takes four to six weeks.¹⁰

If you’ve lost your EIN, check the original CP 575 notice, a prior business tax return, or records at the bank where you opened your business account. State or local licensing agencies may also have it on file. As a last resort, call the IRS Business and Specialty Tax Line at 800-829-4933, Monday through Friday, 7:00 a.m. to 7:00 p.m. local time. The IRS will verify your identity and give the number over the phone to an authorized person.⁸

1
U.S. Small Business Administration. Get Federal and State Tax ID Numbers
2
Internal Revenue Service. Employer Identification Number – Section: Who Needs an EIN
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Internal Revenue Service. Get an Employer Identification Number
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Internal Revenue Service. Single Member Limited Liability Companies
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Internal Revenue Service. Instructions for Form SS-4 (Rev. December 2025)
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Internal Revenue Service. Responsible Parties and Nominees
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Internal Revenue Service. Instructions for Form SS-4 – Section: How To Apply for an EIN
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Internal Revenue Service. Employer Identification Number
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Internal Revenue Service. When To Get a New EIN
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Internal Revenue Service. Form 8822-B, Change of Address or Responsible Party — Business